In the north are savage peaks, to the south gently rolling lowlands. The Isle of Arran is Scotland in miniature - and British gem, writes Graham Hoyland.

The odd thing about islands is that you keep going back to them. I was conceived on the Isle of Arran, and I suppose I will keep returning until I die. Our family decamped there every summer holiday, coming up from England to stay with my grandmother. We didn't live in the Front House, her solid sandstone terraced house in Brodick, but squatted in the Back, a tiny, two-room cottage with wooden cabins behind it in another, recessive Back. Grandmother came too. From here, in an atmosphere of paraffin lamps and the smell of damp, come my oldest memories of Arran.

The reason for my grandmother's seasonal move was to make room for the Folk. Nearly everyone in Arran seemed to let their houses to the holiday- makers from Glasgow. Standing in the Firth of Clyde has truly made Arran "Scotland's holiday island", but somehow its very popularity blinds people to the fact that this is one of the real gems of the British Isles.

Robert Burns seemed blind to Arran, too. He must have seen the Arran hills from the inland Ayrshire farms where he spent his youth, but he fails to mention the island in his writings. This seems unaccountable; as you arrive at the dismal town of Ardrossan to catch the ferry you cannot fail to be impressed by the view across 14 miles of sea - if it's not raining. Then you may just see a dirty grey smudge. But on a clear day, Arran floats there in all her glory.

At once you can see why the island claims to be a Scotland in miniature. In the north, savage peaks jag against the sky, their flanks streaked with white burns. In the middle the glens dip down to Brodick, the main village, and to the south are the softly rolling lowlands, interrupted by the shape of Holy Isle.

You can take your car on to the ferry, or, better still, your bike. As the ferry approaches Brodick Bay on the eastern side of the island you may see measured mile markers further up the coast. The Clyde-built liners used to time their trials speed against them; this stretch of water is where they first stretched their sea-legs.

Arran is immeasurably ancient; it was an island before the mainland of Britain parted company with Europe. We know this because its spectacular physical structure was the battleground of the early geologists, the Neptunists versus the Plutonists. The views of the latter prevailed: it is now believed that the northern granite peaks were the result of an upwelling of molten material from the Earth's interior, since eroded by time - and the hammers of generations of geology students, who have come every summer to chip away at the 500-million-year-old bones of the island.

As the ferry ties up alongside Brodick pier you can see that the coast road goes in two directions - of course, it's circular. It's 56 miles round the island, and it can be cycled in a day. It's also a great way to see Arran. If you go northabout you do the difficult bits first. You pedal through Brodick, around the broad bay named by the Vikings, perhaps gazing up at Goatfell, the highest mountain of the island. Just under 3,000ft, it's not big enough to qualify for the Munro system, which suggests that only mountains over that height are worth climbing. This serves to point out the absurdity of a system based on size.

Arran's mountains are some of the finest in the world, being finely shaped, accessible in a day and surrounded by sea. Across the bay, beneath Goatfell, is Brodick Castle, a red sandstone symbol of the power of the feudal system, repeatedly sacked and rebuilt. A study of its blood-soaked history leaves you feeling rather grateful for living in our own age.

One of the absentee landlords, the 12th Duke of Hamilton, preferred to carouse in Nice with his expensive mistress, Amelia Gioia, on an income of pounds 140,000 a year. Meanwhile his tenants were being thrown off the land to make room for the cost-effective black-faced sheep. Now you can enjoy tea while admiring the castle gardens, which have fine rhododendrons.

Pedalling up the coast, you pass through Corrie, reckoned by Asquith to be the prettiest village in Europe, and home to the founder of the publishing Macmillans. For one bizarre moment you double-take, and then realise that the bollards of the tiny harbour are painted to look like sheep. Black-faced sheep. Looking left as you pass through Sannox you can see right up Glen Sannox to Cir Mhor, a dramatic mountain view. It's a struggle up and over the Boguille, where the road leaves the coast and takes to the hills, but behind you'll see a great jagged ridge, with the terrible Witch's Leap.

"Arran of the many stags," declaimed a Gaelic poet; at this time of year you may see a stag rendered black and frightening by wallowing in the peat bogs. Then it's a long, winding free-wheel into Lochranza with its grim castle, and views of the Mull of Kintyre.

Now the road turns south along the flat shoreline of the west coast. Remote and sparsely populated, this side of the island feels Hebridean. Past a row of white cottages at Catacol, wonderfully named the Twelve Apostles, and past the guest house still run by members of my family. Up the glen is to be found a species of service tree unique to Arran. I remember going on an exhausting expedition up there with my father to find one, while my mother - another native of the island - found a tree by the road after a leisurely lunch.

It's easy pedalling on this side of Arran; your tyres sing as you cycle on the polished Tarmac and it can feel surprisingly lonely. The sky seems huge; the oystercatchers whistle along the shore. Nothing much has changed here for thousands of years, and the great stone circles at Machrie remind you of the ancient owners of this land.

The names slip by: Torbeg, Drumadoon and Sliddery Water. Suddenly you find yourself in a tropical rain-forest. Appropriately, Lagg is at the southern end of the island; the palm trees and lush undergrowth are an indication of the warmth of the Gulf Stream that washes around the island. Tea at the hotel here is timely, as now you are returning northwards.

In Whiting Bay you will pass the Burlington Guest House, where I had the best meal I've ever had on the island. Now Holy Isle is coming into view in the huge, natural anchorage of Lamlash bay. Saint Molaise lived here in a cave (as was fashionable in the sixth century), and for hundreds of years Holy Isle was a place of Christian pilgrimage. Now it is owned by a sect of Tibetan Buddhists who want to make the island-within-an- island a world centre for ecumenical, ecologically friendly contemplation. They have already planted 30,000 trees and have plans for a multi-million- pound retreat complex sunk into the hillside.

Abbot-Lama Yeshe Losal's cell will be at the top, reached by a winding path, and glass-fronted individual cells will cascade downwards in two tiers, one for men, one for women. Each cell echoes St Molaise's cave, but will include a lavatory and shower. The Buddhists are trying to leave their Wheel of Life to reach a finer place, but as we gasp over the hill from Lamlash we have come full circle on our journey.

Now we can speed back down to Brodick pier. The northern hills look good from up here, frozen in a snapshot from their million-year lives. This is what Arran so powerfully evokes: the infinity of time. We are just shadows that flit across the land; all we can do is celebrate it.

Getting there: Most ferry services are operated from Ardrossan to Brodick by Caledonian MacBrayne (enquiries, 01475 650100; bookings, 0990 650000), with three ferries each way each day; from Ardrossan at 9.45am, 3.15pm and 6pm, and from Brodick at 8.20am, 1.50pm and 4.40pm. The foot passenger fare is pounds 5.35 for a five-day return. A five-day return for a regular-sized car costs pounds 39.50. A bicycle costs pounds 2 return.

Accommodation: Graham Hoyland's relations run the Fairhaven Guest House in Catacol (01770 830237). For other places to stay, call the tourist information office in Brodick (01770 302140).